Filter
Top Products
CHAPTER 4 PORT FUNCTIONS
User’s Manual U12978EJ3V0UD
69
4.3 Registers Controlling Port Function
The following three types of registers control the ports.
• Port mode registers (PM0, PM1, PM2, PM4)
• Pull-up resistor option register (PU0)
• Port output mode registers (POM0, POM1)
(1) Port mode registers (PM0, PM1, PM2, PM4)
These registers are used to set port input/output in 1-bit units.
The port mode registers are independently set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets registers to FFH.
When port pins are used as alternate-function pins, set the port mode register and output latch according to
Table 4-3.
Caution As P26 can be used as an external interrupt input, when the port function output mode is
specified and the output level is changed, the interrupt request flag is set. When the
output mode is used, therefore, the interrupt mask flag should be set to 1 beforehand.
Figure 4-11. Format of Port Mode Register
PMmn
0 Output mode (output buffer on)
Input mode (output buffer off) 1
PM07
1
PM06
PM26
PM05
PM25
PM04
PM24
PM03
PM23
PM02
PM22
PM01
PM21
PM00
PM20
PM0
PM2
7
Symbol Address After reset
6543210 R/W
FF20H
FF22H
FFH
FFH
R/W
R/W
PM47 PM46 PM45 PM44 PM43 PM42 PM41 PM40
PM4
FF24H FFH R/W
Pmn pin input/output mode selection
PM17 PM16 PM15 PM14 PM13 PM12 PM11 PM10PM1
FF21H FFH R/W